AesCtr class abstract

AES-CTR (counter mode) Cipher.

In browsers, the default implementation will use Web Cryptography API. On other platforms, DartAesCtr will be used.

If you use Flutter, you can enable cryptography_flutter. It can improve performance in many cases.

Things to know

  • Three possible key lengths:
  • Nonce length is 12 bytes by default, which implies 4 bytes for the block counter. Because block is 16 bytes, the maximum message size is 32 GB with a single nonce. You can choose another nonce length in the constructor if you need to support larger messages.
  • You must choose some macAlgorithm. If you are sure that you don't need one, use MacAlgorithm.empty.

Example

import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  final message = <int>[1,2,3];

  // AES-CTR with 128 bit keys and HMAC-SHA256 authentication.
  final algorithm = AesCtr.with128bits(
    macAlgorithm: Hmac.sha256(),
  );
  final secretKey = await algorithm.newSecretKey();
  final nonce = algorithm.newNonce();

  // Encrypt
  final secretBox = await algorithm.encrypt(
    message,
    secretKey: secretKey,
  );
  print('Nonce: ${secretBox.nonce}')
  print('Ciphertext: ${secretBox.cipherText}')
  print('MAC: ${secretBox.mac.bytes}')

  // Decrypt
  final clearText = await algorithm.encrypt(
    secretBox,
    secretKey: secretKey,
  );
  print('Cleartext: $clearText');
}
Inheritance
Implementers

Constructors

AesCtr.constructor({Random? random})
Constructor for classes that extend this class.
const
AesCtr.with128bits({required MacAlgorithm macAlgorithm})
Constructs 128-bit AES-CTR.
factory
AesCtr.with192bits({required MacAlgorithm macAlgorithm})
Constructs 192-bit AES-CTR.
factory
AesCtr.with256bits({required MacAlgorithm macAlgorithm})
Constructs 256-bit AES-CTR.
factory

Properties

counterBits → int
Number of bits occupied by the counter.
no setter
hashCode → int
The hash code for this object.
no setteroverride
macAlgorithm → MacAlgorithm
Message authentication code (MacAlgorithm) used by the cipher.
no setterinherited
nonceLength → int
Number of bytes in the nonce ("Initialization Vector", "IV", "salt").
no setteroverride
random → Random?
Random number generator used by newSecretKey for generating secret keys.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
secretKeyLength → int
Number of bytes in the SecretKey.
no setterinherited

Methods

checkParameters({int? length, required SecretKey secretKey, required int nonceLength, int aadLength = 0, int keyStreamIndex = 0}) → void
Checks parameters for encrypt / decrypt and throws ArgumentError if any is invalid.
override
cipherTextLength(int clearTextLength) → int
Calculates the length of the ciphertext given a clear text length.
inherited
decrypt(SecretBox secretBox, {required SecretKey secretKey, List<int> aad = const <int>[], int keyStreamIndex = 0, Uint8List? possibleBuffer}) → Future<List<int>>
Decrypts a ciphertext.
inherited
decryptStream(Stream<List<int>> stream, {required SecretKey secretKey, required List<int> nonce, required FutureOr<Mac> mac, List<int> aad = const [], bool allowUseSameBytes = false}) → Stream<List<int>>
Decrypts a Stream of bytes.
inherited
decryptString(SecretBox secretBox, {required SecretKey secretKey}) → Future<String>
Calls decrypt and then converts the bytes to a string by using utf8 codec.
inherited
encrypt(List<int> clearText, {required SecretKey secretKey, List<int>? nonce, List<int> aad = const <int>[], int keyStreamIndex = 0, Uint8List? possibleBuffer}) → Future<SecretBox>
Encrypts a cleartext.
inherited
encryptStream(Stream<List<int>> stream, {required SecretKey secretKey, required List<int> nonce, required void onMac(Mac mac), List<int> aad = const [], bool allowUseSameBytes = false}) → Stream<List<int>>
Encrypts a Stream of bytes.
inherited
encryptString(String clearText, {required SecretKey secretKey}) → Future<SecretBox>
Converts a string to bytes using utf8 codec and then calls encrypt.
inherited
newCipherWand() → Future<CipherWand>
Constructs a CipherWand that uses this implementation and a new random secret key (that can't be extracted).
inherited
newCipherWandFromSecretKey(SecretKey secretKey, {bool allowEncrypt = true, bool allowDecrypt = true}) → Future<CipherWand>
Constructs a CipherWand that uses this implementation and the given SecretKey.
inherited
newNonce() → List<int>
Generates a new nonce.
inherited
newSecretKey() → Future<SecretKey>
Generates a new SecretKey.
inherited
newSecretKeyFromBytes(List<int> bytes) → Future<SecretKey>
Constructs a new SecretKey from the bytes.
inherited
newState() → CipherState
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
override
toSync() → DartAesCtr
Returns a synchronous, pure Dart implementation of this cipher.
override

Operators

operator ==(Object other) → bool
The equality operator.
override

Constants

defaultCounterBits → const int
Default value for counterBits.